/* estPi.cpp
 *
 * This program calculates Pi using random numbers.
 *
 * Bruce M. Bolden
 * October 14, 1997
 * ---------------------------------------------------------
 */

#include <iostream.h>
#include <iomanip.h>
#include <stdlib.h>
#include <time.h>

    //  Prototypes
double GetXY();
void   GetXY( double& x, double& y );

int    IsInside( double x, double y );
void   InitRandomNumberGenerator();


int main()
{
    //InitRandomNumberGenerator();
    
    char  ans = 'y';          //  response to continuation question

    do
    {
        int  nHits = 0;       //  number of "hits"
        int  nTries;          //  number of attempts
        double  x, y;         //  coordinates of random point
 
            //  Prompt for number of attempts
        cout << "Number of tries: ";
        cin >> nTries;

            //  Generate points, test if inside unit circle
        for( int i = 0; i < nTries ; ++i )
        {
            //x = GetXY();
            //y = GetXY();
            GetXY( x, y );    //  pass by reference
        
            if( IsInside( x, y ) )
               ++nHits;
        }

        cout << "nHits: " << nHits << endl;

             //  Show results
        double pi = 4.0 * nHits/nTries;
        cout << " Pi: " << pi << endl;
        
             //  Ask if user wants to continue
        cout << "Again [y/n]? ";
        cin >> ans;
    }
    while( ans != 'n' && ans != 'N' );

    return 0;
}


/*  GetXY()
 *
 *  Generate a random value between 0.0 and 1.0.
 */

double GetXY()
{
    double rVal = double(rand()) / double(RAND_MAX);

    //double rVal = double(rand() % 101) / 100.0;
    //cout << rVal << endl;     //  check values

    return rVal;
}

void GetXY( double& x, double& y )
{
    x = double(rand()) / double(RAND_MAX);
    y = double(rand()) / double(RAND_MAX);

    //  Old method
    //x = double(rand() % 101) / 100.0;
    //y = double(rand() % 101) / 100.0;
}



/*  IsInside
 *
 *  Test if a point (x,y) lies inside the unit circle
 */

int IsInside( double x, double y )
{
    if( x*x + y*y <= 1.0 )
        return 1;
    return 0;
}


/*  InitRandomNumberGenerator
 *
 *  Initialize random number generator.
 */

void InitRandomNumberGenerator()
{
    /* Seed the random-number generator with current time so
     * that the numbers will be different each time program is run.
     */
    srand( (unsigned)time( NULL ) );
}